marketrent OP t1_it7k5t8 wrote on October 21, 2022 at 2:40 PM

Papers published 20 October 2022:

>First asteroid gas sample delivered by the Hayabusa2 mission: A treasure box from Ryugu

>https://www.science.org/doi/10.1126/sciadv.abo7239

>Abstract

>The Hayabusa2 spacecraft returned to Earth from the asteroid 162173 Ryugu on December 6, 2020. One day after the recovery, the gas species retained in the sample container were extracted and measured on-site, and stored in gas collection bottles. The container gas consists of helium and neon with an extraterrestrial 3He/4He and 20Ne/22Ne ratios, along with some contaminant terrestrial atmospheric gases. A mixture of solar and Earth’s atmospheric gas is the best explanation of the container gas composition. Fragmentation of Ryugu grains within the sample container is discussed based on the estimated amount of indigenous He and the size distribution of the recovered Ryugu grains. This is the first successful return of gas species from a near-Earth asteroid.

and

>Noble gases and nitrogen in samples of asteroid Ryugu record its volatile sources and recent surface evolution

>https://www.science.org/doi/10.1126/science.abo0431

>Abstract

>The near-Earth carbonaceous asteroid (162173) Ryugu is expected to contain volatile chemical species that could provide information on the origin of Earth’s volatiles. Samples of Ryugu were retrieved by the Hayabusa2 spacecraft. We measure noble gas and nitrogen isotopes in Ryugu samples, finding they are dominated by pre-solar and primordial components, incorporated during Solar System formation. Noble gas concentrations are higher than those in Ivuna-type carbonaceous (CI) chondrite meteorites. Several host phases of isotopically distinct nitrogen have heterogeneous abundances between the samples. Our measurements support a close relationship between Ryugu and CI chondrites. Noble gases produced by galactic cosmic rays, indicating ~5 Myr exposure, and from implanted solar wind, record the recent irradiation history of Ryugu after it migrated to its current orbit.

shiruken t1_it81rou wrote on October 21, 2022 at 4:37 PM

This is the actual paper referenced by the press release. It does look like several papers on Ryugu were simultaneously published yesterday.

>Ryugu's nucleosynthetic heritage from the outskirts of the Solar System
>
>https://www.science.org/doi/10.1126/sciadv.add8141

marketrent OP t1_it82c9m wrote on October 21, 2022 at 4:41 PM

Thanks! (The press release didn’t include hyperlinks.)

>Abstract

>Little is known about the origin of the spectral diversity of asteroids and what it says about conditions in the protoplanetary disk. Here we show that samples returned from Cb-type asteroid Ryugu have Fe isotopic anomalies indistinguishable from Ivuna-type (CI) chondrites, which are distinct from all other carbonaceous chondrites. Iron isotopes, therefore, demonstrate that Ryugu and CI chondrites formed in a reservoir that was different from the source regions of other carbonaceous asteroids. Growth and migration of the giant planets destabilized nearby planetesimals and ejected some inwards to be implanted into the Main Belt.

>In this framework, most carbonaceous chondrites may have originated from regions around the birthplaces of Jupiter and Saturn, while the distinct isotopic composition of CI chondrites and Ryugu may reflect their formation further away in the disk, owing their presence in the inner Solar System to excitation by Uranus and Neptune.